1. Field of the Invention
The invention relates to memory refresh methods and devices, and in particular to the methods and devices to switch each memory rank of a memory to a self-refresh mode respectively.
2. Description of the Related Art
A system memory stores data from a central processing unit (CPU) and various peripheral components. Usually, as capacity of a system memory increases, power consumption increases accordingly. One commonly used system memory is a dynamic random access memory (DRAM), embodies as a single in-line memory module (SIMM) or dual in-line memory module, (DIMM), with channels referred to as memory ranks. Memory usually comprises a plurality of memory banks, each comprising multiple memory cells arranged in arrays.